NOGALES, Ariz. -- Hundreds of Mexican nationals who wear government-issued uniforms, carry official identification cards and are authorized to use weapons are helping smugglers move tons of drugs into the United States, U.S. law-enforcement officials say.

Known as "madrinas," from the Spanish word for "godmothers," they negotiate bribes for corrupt Mexican government officials from drug cartels and are suspected in numerous confirmed incursions into the U.S. by heavily armed men escorting smugglers of cocaine, marijuana and heroin.

"Madrinas are unaccountable middlemen who can negotiate with the drug cartels on behalf of whoever has appointed them and wants his or her government agency to thrive under this practice," El Paso County, Texas, Sheriff Leo Samaniego told a House committee last month.